1. Field of the Invention
The present invention relates to an image processing system for compressing an input image signal, and more particularly, to an apparatus and method for correcting a motion of an image, which occurs due to a shake of a hand or vibration of a system, thereby increasing efficiency in compressing an image signal.
2. Description of the Related Art
Image processing systems that users can carry with them to collect image signals need a function of correcting a motion of an image, which occurs due to a shake of a hand or vibration of a system including image processing systems. This is because it is highly likely that a hand shake or vibration of a system occurs while portable image pickup apparatuses are used to collect image signals. If a hand shake or vibration of a system occurs when collecting image signals, an image is recognized as having a motion even if the image has no motion. Accordingly, image processing systems need a function of correcting a motion of an image. For example, video cameras may be included in such image processing systems.
A motion correction function provided for conventional video cameras detects the amount of vibration of a camera using a vibration sensor and moves an image on a lens up, down, to the left, or to the right based on the amount of vibration, thereby correcting the motion of the image. Video cameras can compress a motion-corrected image signal and store or transmit the compressed image signal to another apparatus. Most video cameras compress an image signal using an intra coding method. In the intra coding method, an input image signal is compressed regardless of the correlation with another image.
As described above, conventional video cameras do not consider the correlation between frames when correcting a motion occurring due to a shake of hand or vibration of a system and when compressing an image signal. Accordingly, conventional video cameras have a limitation in collecting a large volume of images, such as a motion picture.
To overcome this problem, there have been attempts to apply a compression method, such as the Moving Picture Experts Group standards, (MPEG)-2 or MPEG-4, using both intra coding method and inter coding method to image processing systems such as video cameras. In case of using MPEG-2 or MPEG-4 as a compression method, if an image signal, for which motion occurring due to a shake of a hand or vibration of a system has been corrected as described above, is used, a compression efficiency for the image signal may be decreased in an inter coding mode. This is because the motion correction is performed in units of scenes without considering the correlation of the image signal with another image, whereas a motion is estimated and corrected considering the correlation between a current frame and a previous frame, and a difference image resulting from the motion estimation and correction is compressed in the inter coding mode.